1. Field Of The Invention
This invention relates generally to non-rotatable telescoping support structures, and more particularly to a support structure which is readily adaptable for use in a pole lamp wherein the electrical wires are disposed within the telescoping members and relative rotation between the members is prevented to deter damage to the electrical wires.
2. Prior Art
Gindel, U. S. Pat. No. 4,238,818 discloses a non-rotatable telescoping support structure which includes an outer elongated tubular member of substantially cylindrical shape and an inner elongated member having a portion of reduced radial size with respect to the longitudinal central axis of the inner member. The outer cylindrical member has a protuberance extending inwardly beyond the inner surface of the outer member. The protuberance is aligned with the area of reduced radial size of the inner member so that the inner member can slide longitudinally relative to the outer member. However, if relative rotation between the members is attempted, the protuberance engages the surface of reduced radial size of the inner member. A cylindrical outer end surface of the outer member is threaded to accept a split ring assembly which may be tightened on the threads to prevent longitudinal movement between the inner member and the outer member. While under normal conditions the Gindel system does deter relative rotation of the members, it is possible, with force, to push the protuberance outward and enable the inner member to be rotated within the outer member.
Another non-rotatable telescoping support structure is shown in Thines, U.S. Pat. No. 2,445,543. This structure is designed to support the roof of a mine shaft and includes a locking collar which automatically locks the inner and outer telescoping components as the inner component is extended out of the outer component. Outward extension of the inner component is permitted but the inner component cannot be slid back into the outer component without unlocking the collar. Since the structure supports considerable weight, the inner and outer components are square in cross section to provide a large area of friction between the inner component and the locking collar. The locking collar merely rides on the upper end of the outer component and is not secured to the outer component either by threading or any other means.